摘要：The Greater Mekong Subregion is a transnational area bound together by the Mekong River basin and its immense hydropower resources, historically seen as the backbone of regional economic development. The basin is now punctuated by several dams, successful in attracting both international investors and fierce criticisms for their environmental and societal impacts. Surprisingly, no attention has been paid so far to the actual performance of these infrastructures: is hydropower supply robust with respect to the hydroclimatic variability characterizing Southeast Asia? When water availability is altered, what are the implications for power production costs and CO 2 emissions? To answer these questions, we focus on the Laotian–Thai grid—the first international power‐trade infrastructure developed in the region—and use a power system model driven by a spatially distributed hydrological‐water management model. Simulation results over a 30‐year period show that production costs and carbon footprint are significantly affected by droughts, which reduce hydropower availability and increase reliance on thermoelectric resources. Regional droughts across the Mekong basin are of particular concern, as they reduce the export of cheap hydropower from Laos to Thailand. To put the analysis into a broader climate‐water‐energy context, we show that the El Niño Southern Oscillation modulates not only the summer monsoon, but also the power system behavior, shaping the relationship between hydroclimatological conditions, power production costs, and CO 2 emissions. Overall, our results and models provide a knowledge basis for informing robust management strategies at the water‐energy scale and designing more sustainable power plans in the Greater Mekong Subregion. Plain Language Abstract The development of hydropower dams in the Mekong River basin has historically been seen as a means to support economic growth in Southeast Asia. Because water availability varies on both seasonal and interannual time scales, we hypothesized that an unstable supply of hydroelectricity may temporarily increase reliance on gas and coal, thereby affecting power production costs and carbon footprint. To verify this hypothesis, we developed a coupled water‐energy model of the Laotian‐Thai grid, the largest power infrastructure in the region. The model represents the relationship between hydroclimatological conditions, water availability, and power system behavior. Simulation results show that prolonged droughts in the Mekong basin reduce hydropower production by about 4,000 GWh/year, increasing the annual production costs and CO 2 emissions by about US$ 120 millions and 2.5 million metric tonnes, respectively. These events are largely explained by the periodic oscillations in the tropical eastern Pacific Ocean that modulate water availability in Southeast Asia. Our findings can help reduce the carbon footprint of power systems and inform the design of hydroelectric dams.
